Positioning mechanism



May 6, 1958 G. J. KENNEDY ErAx. bPosITIoNING 'MECHANISM' 2 Sheets-Sheetl ,ud Hnudnnvn Filed July 15, 1955 IHHHMUHH Illll'nllll' nl May 6, 1958G. J. KENNEDY l-:TAL 2,833,976

PosITIoNING MECHANISM Filed July 15, 1955 2 Sheets-Sheet 2 ill V IN VENTORS WMM/2.0 nf. 00x; BY

i AGE/Vf POSITIONING MECHANISM Gilbert J. Kennedy, Philadelphia, andWinfield W. Loose,

Reading, Pa., assignors to Philco Corporation, Philadelphia, Pa., acorporation of Pennsylvania Application July 15, 1955, Serial No.522,293

4 Claims. (Cl. S18-467) This invention relates to motorized positioningmechanisms, and more particularly to ratchet stepping mechanisms forpositioning a rotary device by moving it in a .step-by-step fashion.

The invention has as its broad and primary object to provide a novel andsimple electromechanical mechanism for operating a rotary devicestep-by-step through predetermined sequential angular increments. Y

Another object of the invention is the provision of such a positioningmechanism which is automatically responsive to momentary closing of acontrol switch to operate a rotary device, moving it from one positionto another, and then to shut itself ofi.

A further object of the invention is to provide a ratchet lsteppingmechanism which will self-cycle or step through a number of positionsautomatically.

It is also an object of the invention to provide such apparatus in whichthe rotary device is capable of being selectively operated eitherelectrically or manually.

A specific object of the invention is the provision of a self-cyclingratchet stepping device adapted for remote control, and in which asingle control impulse from a remote switch will cause the mechanism tostep, or cycle, until a desired predetermined position is reached.

More specifically, it is an object of the invention to provide apparatusembodying the broad concepts of the invention and particularly suitedfor remote actuation of channel selector switches in televisionreceivers.

Another specific object of the invention is to provide such apparatuswhereby channel selection is predetermined, yet easily changeable, asdesired.

A further and still more specific object of the invention is to providemechanism of the above-stated type which is simple in construction andoperation, easy to adjust, yet is characterized by rugged construction.

In accordance with the present invention, and rst briefly described, themechanism includes a motorized self-cycling stepping ratchet wheelwhich, in response to momentary closing of a starting switch in a powersupply circuit, is moved sequentially and step-by-step throughpredetermined angular increments by a motor actuated pawl, each angularincrement in the illustrated embodiment corresponding to a differenttelevision channel. Indexing stops or pins, at preselected positions onthe ratchet wheel, operate mechanism controlling a holding switch in themotor circuit to retain the circuit closed during self-cycling of theratchet wheel, and to shut off the motor when the ratchet wheel isstepped to the next preselected position or channel. Means is providedfor stopping operation of the actuating mechanism at a predeterminedinitial oi rest position whereby sequential cycles thereof all start atthe same position.

The invention may be clearly understood from the following detaileddescription with reference to the accompanying drawings, wherein:

Figure 1 is an elevational view of apparatus embodying the concepts ofthe invention (the motor not being shown) and showing the device in itsrest or starting position;

" nited States Patent O 2,833,976` latented May 6, 1958 ICC Figures 2,3, 4, 5 and 6 are views similar to Figure l, but showing sequentialoperational conditions of the apparatus;

Figure 7 is a top plan view of the apparatus; and

Figure 8 is a circuit diagram.

While in its broader aspects, `as mentioned above, the invention isapplicable to any appropriate device, the following description is inconnection with its use as an operating agency for rotary switches ofthe type used for channel selection in television receivers.

As viewed in Figure 1, the apparatus comprises a base plate 9 havingjournalled therein a shaft 10 carrying a stepping ratchet wheel 11provided with a number of te/eth 12, corresponding to the number ofavailable V. H. F. television channels. Ratchet wheel 11 is pro videdadjacent each tooth 12 with an aperture 13 adapted to receive indexingstops or pins 14, one being shown in each of the apertures designatingchannels 3, 6 and 10.

Also journalled in base plate 9, upon a shaft 15, is a drive gear 16arranged to be rotated by motor .17, Figure 7, through pinion 18. Thedrive engagement between the motor and the pinion may be of anywellknown type but, as shown, comprises driving element 19 and drivenelement 20, element 19 being secured to the motor shaft 21 while element20 is formed integrally with pinion 18, the latter being mounted forfree rotation upon extension 22 of the motor shaft 21. The motor shownis of the type having an offset motor which, when the motor isenergized, centers itself relative to the stator, moving element 19forwardly in a position to engage element 20 and thereby rotate pinion18 to drive gear 16.

Journalled on a shaft 24, carried by gear 16 eccentrically of gear shaft15, is a pawl 25 held against the gear under spring tension, as byspring washer 26, and normally tending to rotate counter-clockwise, withgear 16. However, the pawl is provided with an outturned end portion 27,indicated in dotted line, which engages a cam surface 28 formed on oneside of a slot or aperture 29 in base plate 9, and4 thus is guided intoengagement with the teeth on the ratchet wheel, the extent of theswinging movement of the pawl being determined by the width of slot 29.l

Also journalled on base plate 9, as by shaft 30, is suitable lever meanswhich, in the present embodiment comprises rocker-arm or bell crank 31including arm elements 32 and 33. Element 33 is independently journalledon shaft 30 over element 32 but is releasably held against the lowerportion 34 of element 32 by spring 35. One end of spring 35 is connectedto a lateral extension 36 at the lower end of the link 33, and its otherend connected to a portion 33a of arm 34 bent around the lower left-handedge of link 33. The bell crank has been constructed in this manner toprovide independent movement of link 33, if for some Lreason bell crank31 fails to function properly while the ratchet wheel is being rotated.

It will be noted that link 33 of the bell crank is provided on itsleft-hand edge with a cam portion 37, the purpose of which will beexplained later. The upper end of the bell crank is bifurcated,providing a recess 38 and two linger elements 39 and 40. A circuitholding switch 41 including a resilient contact element 42 and a fixedcontact member 43 is mounted on panel 9 with the end of contact element42 extending into recess 38.

AFinger 40 is provided with an outwardly turned cam follower or lug 44which, as shown in Figure l, is normally engaged by a cam surface ortrack 45 formed 4by a depending portion of gear 16. Lug 44 is shown, inFigure l, in a generally central position relative to the cam surface,the latter being formed with an arcuate central portion and outwardlyared end portions.

Also journalled on shaft 30 is a link 46 extending to the left beneathgear 16. The link is provided in an edge portion thereof with a detent47 releasably engaging a pin 48 depending from the inner side of gear16. The .link is biased clockwise against pin 48 as by spring 49. InFigure 1, the pin is shown at the bottom of detent 47 thus positioningthe mechanism in its rest or starting position.

Shaft is provided with extensions 50 and 51, shown in broken lines inFigure 1. Aknob 52 is shown attached to the end of shaft extension 50for manually rotating the channel selector switch (not shown) in thetuner housing indicated by the numeral 53 at the end of shaft extension51.

Motor 17, as shown in Figure 8, may be connected in circuit with asuitable source of energy, identified by the letter 1., through holdingswitch 41 Aand/or manually operable control switches 54 and 55. Switch54 may be mounted on the cabinet of the television receiver, whileswitch 55 may be situated at a position removed from the receiverthereby enabling the motor to be energized from a remote position. Whileonly two operating switches have been shown, it is understood that anyconvenient number may be provided.

In the operation of the apparatus described above,

either one of switches 54 or 55 (Figure 8) may be closed f momentarilyto energize motor 17, at which time armature 23 centers itself relativeto the stator, moving shaft 21 forwardly to engage driving element 20,as is clearly shown in Figure 4, and rotate gear 16 in acounterclockwise direction. It will be seen from Figure 1, showing themechanism in the rest or starting position, that carn follower 44 ofbell crank 31 is engaging cam surface 45, and nger 39 is holding switch41 open, while cam portion 37 of link 33 is held slightly spaced to theright of the indexing pin 14, at channel 3. Also, pawl is in itsretracted position at the upper end of the cam slot 29 in base 9. Whenthe mechanisms are in this condition it will be seen that ratchet Wheel11 is free to be rotated in either direction, thus permitting manualtuning, as by knob 52, if desired.

Upon momentary closing of either of switches 54 or 55, as mentionedabove, gear 16 is rotated in a counterclockwise direction. When it hasrotated through approximately 90, as shown in Figure 2, cam follower 44has been released from cam track 45, permitting arm 32 of bell crank 31to be moved in a clockwise direction by spring 56, permitting holdingswitch 41 to close, and moving cam portion 37 on link 33 against pin 14at channel 3. Pawl 25 is now engaging the tooth 12 opposite the aperture13 at channel 9. It will be understood that the condition shown inFigure 2 is arrived at almost instantaneously with the momentary closingof either of switches 54 or 55. Note thatthe holding switch 41 now isclosed and therefore the starting switch may be released withoutstopping the operation of motor 17.

Continued rotation of gear 16, as shown in Figure 3, urges pawl 25 toits completely advanced position to rotate the ratchet wheel 11 throughone angular increment, indicated at A. This moves the indexing pin 14 atchannel 3 away from cam portion 37 of arm 33, bringing the emptyaperture 13, at channel 4, opposite the cam portion, and permitting thelatter to move into Vthe path of rotative movement of the next indexingpin,

at channel 6.

A single complete rotation, or cycle, of gear 16 is illustrated inFigure 4. Pawl 25 is again in its retracted position with its end 27moved, as guided by cam surface 28, out of the path of rotation ofratchet wheel 11. Bell crank 31 has moved in a clockwise direction, andtherefore cam lug 44 on the end of finger 4G is out of the path ofmovement of cam surface 45, and holding switch 41 stays closed, leavingmotor 17 energized. vAs a result, gear 16 is again conditioned to startthrough another cycle of rotation and will move ratchet wheel 11 throughanother angular increment, as described above, wherein the aperture atchannel 5 will be moved opposite to cam portion 37, and, as there hasbeen no movement of the cam follower 44 in a counter-clockwisedirection, completion of the second cycle will see hold* ing switch 41still closed and gear 16 will start another cycle.

With reference to Figure 5, illustrating the condition of the mechanismjust after the beginning of the third cycle, it will be noted that pawl25 is against the tooth 12 opposite channel 11, and cam 37 on link 33 isin contact with the indexing pin 14 at channel 6. Further rotation ofgear 16 moves pawl 25 downwardly to rotate ratchet wheel 11 throughanother increment to the position shown in Figure 6. In reaching thisposition, indexing pin 14 at channel 6 has moved against the cam portion37 rotating the bell crank in a counter-clockwise direction, a distancesuicient to place cam lug 44 in the path of rotation of the ared end ofcam track 45, the latter two elements being shown in Figure 6 at theactual point of contact just prior to completion of the third cycle. Inthis position, finger 39 of link 32 is moving against the flexiblecontact element 42 of switch 41, and pin 48 is approaching detent 47 oflink 46. Continued rotation of the gear causes the cam track to move thebell crank farther in the counter-clockwise direction,- opening switch41 and deenergizing motor 17, however inertia carries the mechanism tothe fully at rest position, illustrated in Figure 1, wherein cam lug 44is in the arcuate portion of cam track 45, and pin 48 is at the bottomof detent 47. The cam surface 45 is so formed as to move the bell crankstill farther in a counterclockwise direction, a distance sufficient todisengage cam 37 from the indexing pin at channel 6 at the completion ofthe cycle, whereby the equipment is conditioned to respond to channel 6and shaft 10 is again free to be rotated manually by knob 52.

Having described the operation of the apparatus as between two spacedchannel positions, its operation between any two predeterminedpositions, as established by pins 14, may be easily understood. t shouldalso be understood that the apparatus may be made to cycle past theindexing pins merely by holding one of switches 54 or 55 closed. Releaseof the switch will cause the mechanism to stop at the next predeterminedposition established by one of pins 14. It will, of course, be clearfrom the foregoing description that selection of the desired channelsrequires nothing more than insertion of the pins 14 in the propercorresponding apertures.

It is evident that various modifications may be made in the structurewithout departing from the invention. For example, the number of teeth13 may be changed, the throw of pawl 25 may be modified, etc., to meetvarious operating conditions, as desired.

We claim:

1. A self-cycling ratchet stepping mechanism, cornprising: a ratchetwheel to be rotated step-by-step through predetermined angularincrements; means for rotating said wheel including, a pawl, a motor,and means interconnecting said pawl and said motor whereby, whenenergized, said motor will drive said pawl through reciprocatorymovements; means for guiding said pawl against said wheel during suchmovement to move said wheel, one increment for each completereciprocation of said pawl; a source of power; a control switch toenergize said motor from said source; a circuit holding switch; a bellcrank; means at predetermined positions on said wheel to condition saidbell crank to open said holding switch; and means operable by said meansinterconnecting said pawl and said motor to effect movement of said bellcrank to open said holding switch and stop operation of said motor.

2. A self-cycling ratchet stepping mechanism, comprising: a wheel havinga plurality of ratchet teeth arranged to be rotated step-hy-step throughpredetermined angular increments, each increment being equal to thedistance ybetween said teeth; means for rotating said wheel, including agear, a pawl carried eccentrically upon said gear, and a motor forrotating said gear to drive said pawl through reciprocatory movement;means for guiding said pawl against said teeth during such movement in amanner to move said wheel one increment for each complete reciprocationof said pawl; a source of power; a circuit connecting said motor to saidpower source; a manually operable switch to close said circuit andenergize said motor; a circuit holding switch; a bell crank; means atpredetermined positions on said wheel to condition said hell crank toopen said holding switch; and means asso* elated with said gear toeffect movement of said bell crank to open said holding switch and stopoperation of said motor.

3. A self-cycling stepping mechanism, comprising: a shaft; a wheelmounted upon said shaft and having a plurality of ratchet teeth deningincrements of rotation; a gear; a motor for driving said gear; a powercircuit for energizing said motor including, a source of electricalenergy, at least one manually operable normally open control switch forclosing said circuit, and an automatically operable holding switch forretaining said circuit closed after said control switch is opened; apawl having one end pivotally mounted upon said gear eccentrically ofthe axis of said gear and its other end arranged to engage said teethwhereby rotation of said gear moves said pawl through reciprocatorymovements between a retracted position away from said Wheel and anadvanced position engaging one of said teeth and moving the wheelthrough one rotative increment; a bell crank; indexing stop means onsaid wheel; a cam track on said gear; cam follower means on one arm ofsaid bell crank releasably engaging said cam track; means on said bellcrank for retaining said holding switch open when said cam follower isso engaged and to close said holding switch when disengaged therefrom;and cam means at the other arm of said bell crank cooperable with saidindexing means to condition said cam follower to re-engage said camtrack and open said holding switch to stop operation of said motor.

4. Apparatus for angularly positioning a rotatable shaft, comprising;drive means releasably coupled to said shaft and adapted to rotate thesame through angular step-bystep increments; motor driven means forimparting the incremental motion to said drive means; switch meansactuatable either to energize or deenergize said motor driven means;indexing means movable in step-by-step iashinn with said shaft; andlever means pivotally mounted intermediate end portions thereof andincluding cam means adiacent one of the end portions operable to actuatesaid switch means to energize the motor driven means, and cam meansadjacent the other of the end portions of said lever means operable bysaid indexing means, when the latter reaches a predetermined position,to provide for actuation of said switch means to deenergize the motordriven means.

References Cited in the iile of this patent UNlTED STATES PATENTS2,646,910 Barnett July 7, 1936 2,409,895 Phelps Oct. 22, 1946 2,433,805Wolit Dec. 30, 1947 2,637,835 Davidson May 5, 1953 2,651,397 MillerSept. 8, 1953 2,689,281 Hooker Sept. 14, 1954 2,798,259 Feldhausen et alMay 1G, 1955

